In this work we have investigated different techniques for generating diffractive optical elements (DOEs) that modify the intensity profile along the axis and the transversal apodization and hiperresolution properties of an optical system. These DOEs have been experimentally implemented by means of a Liquid Crystal Spatial Light Modulator (LCSLM). Firstly, we have designed and implemented non uniform transmission complex pupils, with the aim of modifying the intensity profile along the axis near the image plane of a converging optical system, and obtaining arbitrary profiles with some interesting features. We have proposed a method for designing non uniform transmission pupils which is based on the Fourier Transform relation that exists among the radial complex function of a pupil with axial symmetry and the function that describes the intensity profile along the axis. The method uses an iterative algorithm to obtain the complex pupil function from a desired intensity profile, which have into account the limitations of resolution and size of the LCSLM. It has been tested by computer numerical calculations that the proposed iterative method for designing the complex pupils converges to pupil functions that bring along-the-axis intensity responses which are very similar to the desired intensity profiles. The pupils that have been obtained with the iterative method have been implemented on a phase only LCSLM in order to test their performance in a real optical system. The performance of these pupils has been evaluated by comparing the experimental intensity profile obtained with an optical system in the laboratory with the desired one. The Point Spread Function (PSF) at different transversal planes at different distances along the axis have also been analysed. The results show that the pupils satisfactorily modify the intensity profile along the axis for the tested desired profiles: rectangular profiles of different widths (different depths of focus); a triangular profile; a profile consisting of two rectangles of the same height (double focus); and an asymmetric profile comprising two rectangles of different heights. In the second part of this work, different methods for multiplexing lenses of different powers in the same LCSM are proposed. The intention of these proposals is to achieve a depth of focus increase by overlapping the intensity maxima through the axis. There have been proposed three methods: multiplexing by rings, multiplexing by sectors and random multiplexing. It has been observed that the random multiplexing technique is the most satisfactory for incrementing the DOF of the optical system. This option provides a uniform intensity profile along the whole DOF and a PSF structure which is also uniform along this interval; therefore it is very suitable for image formation of extended objects. It has been studied the random multiplexing performance for obtaining extended images with incoherent illumination. To this end, there have been numerically evaluated the MTF at the best image plane and in defocused planes for different options with the random multiplexing technique. Next, there have been obtained the experimental results for the images of extended objects at different defocused distances and the results have been compared with those for a Fresnel lens with a unique power. It has been observed that the random multiplexing provides satisfactory results, in terms of contrast and resolution, along the whole range of the extended depth of focus.